Saccharin is an artificial sweetener with effectively no food energy which is about 300–400 times as sweet as sucrose or table sugar, but has a bitter or metallic aftertaste, especially at high concentrations. It is used to sweeten products such as drinks, candies, cookies, medicines, and toothpaste.

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Saccharin derives its name from the word "saccharine", meaning "sugary". The word saccharine is used metaphorically, often in a derogative sense, to describe something "unpleasantly over-polite" or "overly sweet".[3] Both words are derived from the Greek word σάκχαρον (sakcharon), which ultimately derives from Sanskrit for sugar, sharkara (शर्करा), meaning "gravel" [3][4]

Saccharin is unstable when heated, but it does not react chemically with other food ingredients. As such, it stores well. Blends of saccharin with other sweeteners are often used to compensate for each sweetener's weaknesses and faults. A 10:1 cyclamate:saccharin blend is common in countries where both these sweeteners are legal; in this blend, each sweetener masks the other's off taste. Saccharin is often used with aspartame in diet carbonated soft drinks, so some sweetness remains should the fountain syrup be stored beyond aspartame's relatively short shelf life. Saccharin is believed to be an important discovery, especially for diabetics, as it goes directly through the human digestive system without being digested.

In its acid form, saccharin is not water-soluble. The form used as an artificial sweetener is usually its sodiumsalt. The calcium salt is also sometimes used, especially by people restricting their dietary sodium intake. Both salts are highly water-soluble: 0.67 g/ml water at room temperature.[5][6]

Saccharin has no food energy. It may trigger the release of insulin in humans and rats, as a result of its taste, but this has not been confirmed in controlled studies.[7][8][9] This is similar for aspartame (another artificial sweetener).[10]

Saccharin was produced first in 1879, by Constantin Fahlberg, a chemist working on coal tar derivatives in Ira Remsen's laboratory at the Johns Hopkins University.[11] Fahlberg noticed a sweet taste on his hand one evening, and connected this with the compound on which he had been working that day.[12][13] Fahlberg and Remsen published articles on benzoic sulfimide in 1879 and 1880.[5][14] In 1884, then working on his own in New York City, Fahlberg applied for patents in several countries, describing methods of producing this substance that he named saccharin.[15] Two years later, he began production of the substance in a factory in a suburb of Magdeburg, Germany. Fahlberg would soon grow wealthy, while Remsen merely grew irritated, believing he deserved credit for substances produced in his laboratory. On the matter, Remsen commented, "Fahlberg is a scoundrel. It nauseates me to hear my name mentioned in the same breath with him."[16]

Although saccharin was commercialized not long after its discovery, until sugar shortages during World War I, its use had not become widespread. Its popularity further increased during the 1960s and 1970s among dieters, since saccharin is a calorie-free sweetener. In the United States, saccharin is often found in restaurants in pink packets; the most popular brand is "Sweet'n Low".

Starting in 1907, the USFDA began investigating saccharin as a direct result of the Pure Food and Drug Act. Harvey Wiley, then the director of the bureau of chemistry for the USFDA, viewed it as an illegal substitution of a valuable ingredient (sugar) by a less valuable ingredient. In a clash that had career consequences, Wiley told President Theodore Roosevelt, "Everyone who ate that sweet corn was deceived. He thought he was eating sugar, when in point of fact he was eating a coal tar product totally devoid of food value and extremely injurious to health." But Roosevelt himself was a consumer of saccharin, and, in a heated exchange, Roosevelt angrily answered Wiley by stating, "Anybody who says saccharin is injurious to health is an idiot."[17] The episode proved the undoing of Wiley's career.

In 1911, the Food Inspection Decision 135 stated that foods containing saccharin were adulterated. However, in 1912, Food Inspection Decision 142 stated that saccharin was not harmful.

More controversy was stirred in 1969 with the discovery of files from the FDA's investigations of 1948 and 1949. These investigations, which had originally argued against saccharin use, were shown to prove little about saccharin being harmful to human health.[citation needed] In 1977, the FDA made an attempt to completely ban the substance.[18][full citation needed] However, this attempt was also unsuccessful, and the sweetener continued to be widely used in the United States. It is now the third-most popular artificial sweetener behind sucralose and aspartame.

In the European Union, saccharin is also known by the E number (additive code) E954.

The current status of saccharin is that it is allowed in most countries, and countries such as Canada have lifted their previous ban of it as a food additive.[19] The claims that it is associated with bladder cancer were shown to be unfounded in experiments on primates.[20] (It is, however, prohibited to mail saccharin tablets or packets to France.)[21]

Saccharin was formerly on California's list of chemicals known to the state to cause cancer for the purposes of Proposition 65, but it was delisted in 2001.[22]

However, in 2000, the warning labels were removed because scientists learned that rodents, unlike humans, have a unique combination of high pH, high calcium phosphate, and high protein levels in their urine.[24][25] One or more of the proteins that are more prevalent in male rats combine with calcium phosphate and saccharin to produce microcrystals that damage the lining of the bladder. Over time, the rat's bladder responds to this damage by overproducing cells to repair the damage, which leads to tumor formation. Since this does not occur in humans, there is no elevated risk of bladder cancer.

The delisting of saccharin led to legislation, known as the Sweetness Act; which was signed into law on December 21, 2000, repealing the warning label requirement for products containing saccharin.[citation needed] In 2001, the U.S. Food and Drug Administration and the state of California reversed their positions on saccharin, declaring it safe for consumption.[26] The FDA's decision followed a 2000 determination by the U.S. Department of Health and Human Services' National Toxicology Program to remove saccharin from its list of carcinogens.

The EPA has officially removed saccharin and its salts from their list of hazardous constituents and commercial chemical products. In a December 14, 2010 release, the EPA stated that saccharin is no longer considered a potential hazard to human health.[27]

Saccharin can be produced in various ways.[28] The original route by Remsen & Fahlberg starts with toluene; another route begins with o-chlorotoluene.[29] Sulfonation by chlorosulfonic acid gives the ortho and para substituted sulfonyl chlorides. The ortho isomer is separated and converted to the sulfonamide with ammonia. Oxidation of the methyl substituent gives the carboxylic acid, which cyclicizes to give saccharin free acid:[30]

The free acid of saccharin has a low pKa of 1.6 (the acidic hydrogen being that attached to the nitrogen).[2] Saccharin can be used to prepare exclusively disubstituted amines from alkyl halides via a nucleophilic substitution,[31] followed by Gabriel synthesis.[32][33]

^(As discussed below, the relative contributions of Fahlberg and Remsen to the discovery were later contested, with no final resolution in sight; the 1879 paper announcing the discovery lists both names as authors, with Fahlberg's name first.)

^Remsen Ira, Fahlberg C. (February 1880). "On the oxidation of substitution products of aromatic hydrocarbons. IV. - On the oxidation of orthotoluenesulphamide". American Chemical Journal1 (6): 426–439. From pages 430-431: "It possesses a 'very marked sweet taste, being much sweeter than cane-sugar'. The taste is perfectly pure. The minutest quantity of the substance, a bit of its powder scarcely visible, if placed upon the tip of the tongue, causes a sensation of pleasant sweetness throughout the entire cavity of the mouth. As stated above, the substance is soluble to only a slight extent in cold water, but if a few drops of the cold aqueous solution be placed in an ordinary goblet full of water, the latter then tastes like the sweetest syrup. Its presence can hence easily be detected in the dilutest solutions by the taste."